Friday, October 21, 2011

De Ente et Essentia and the First Way

Thomas argues in De Ente et Essentia that God is Pure Act, or existence itself subsisting. His metaphysical argument is the ground of the first four of his five ways in proof of God's existence. The argument from motion, the first of these, specifically recalls the transition of a thing's potentiality to actuality. For example, an acorn exists as an acorn in actuality and as an oak tree in potentiality.

Since no potentiality can actualize itself (an acorn needs water, sunlight, etc), it follows that some actuality is needed to actualize a potentiality. Since Pure Act just is existence itself, it's not hard to see why Thomas associates Pure Act with God. All potentialities are possibly actualized, and nothing is actualized apart from Pure Act (existence), so Pure Act ultimately has power over all potentialites and is therefore omnipotent.


  1. There is something I do not understand about these views.
    You say that God is Pure Act. This means that God is devoid of potentiality.
    This must then apply to all attributes that are in the same metaphysical category as potentiality, such as power, disposition, capacity, ability. If I have a potentiality for something, that implies I have the capacity and the power to do it.

    Yet you also say that "Pure Act has the power ....". How can this power be related to the nature of God?
    How can God have a powerful nature, if Pure Act excludes all power in itself?
    How can Pure Act have (in itself) the capacity to do anything?

  2. Hi Ian,

    I think you're reading a modern definition of "potentiality" back into the Aristotelian-Thomistic metaphysics. When Thomas says that God is not composed of any potentiality, he doesn't mean what you and I usually mean in a casual discussion. Potentiality is not the capacity to do something, but rather the inclination toward change. Remember the acorn analogy, in which some existing entity is an acorn in actuality and an oak tree in potentiality. Its exemplification of potentiality means that it can develop into an oak tree upon the actualization of some set of external causes.

    When God is called Pure Act, it's because of his immutability and perfection.

  3. I agree that God has immutability and perfection. We do not need to introduce the word 'potentiality'. You said that 'God is Pure Act'.

    How can 'Pure Act', by virtue of its nature, have any causal powers at all?
    Or: how can causal powers inhere in a being whose nature is Pure Act. It seems to contradict that nature.

  4. Potentiality and actuality are the terms designated to describe a thing's mutability/immutability. Keeping in mind the technical definition of potentiality alluded to above, what is the difficulty in calling Pure Act causally efficacious?

    Maybe if I understood what you mean by "Pure Act," I would be better disposed toward answering your question. I don't want us to be talking past each other.

  5. If something is 'pure act', then it sounds like that it is purely actual, immutable, static, unchanging, and completely determinate in every respect. That it, it has a nature entirely constituted by what is actual and determinate, and it is devoid of what is potential, dispositional, powerful and causal within that nature.
    If something has essential causal powers, for example, it should have causal powers as part of its nature. But to be a causal power contradicts being purely actual. That is because causal powers bring about new things, and therefore what was determinate before is now long true, as now there is something new. That is, causal powers cannot be essential to purely determinate beings, such as a being of pure act.